In the realm of hard drives, adjacent track interference (ATI) is a growing problem. When a particular track on the hard drive is written a large number of times (e.g., 30,000 times or more) without the adjacent track(s) being written, then the data on those adjacent track(s) can become corrupted. This constant overwrite causes some magnetic flux interference on the adjacent tracks that, over many cycles, can accumulate and leave the adjacent tracks unreadable.
For example, consider a track X as having adjacent tracks X+1 and X−1. If track X is written a large number of times before tracks X+1 or X−1 are also written, then the data on X+1 or X−1 could become corrupted. This is a well documented interaction encountered in magnetic recording.
A seemingly simple solution to this problem involves writing the data to the adjacent tracks before the data can become corrupted. However, complications arise in deciding when and how to rewrite the data on these tracks. There is no simple counter of how many times the data at any particular sector is accessed; thus, it is essentially never clearly known as to when interference is about to take place. Currently, there are no known effective solutions to adjacent track interference in use at either the hard drive firmware level or the OS/application/driver level. Inasmuch as the first clear indication of ATI is that data has already become corrupted, it would simply be too late to merely save the data at that point, and the files involved would already be lost.
An aggregating factor with ATI is areal density. As the areal density increases, the physical area containing the data decreases, thus increasing the percentage of area that represents a “fringe” or “border” area with respect to an adjacent track. Since, with ongoing technological developments, there will continue to be a significant increase in the number of tracks, areal density correspondingly increases. As such trends continue among the physical dimensions and physics of media and write mechanisms, the potential for increasing exposure to ATI will correspondingly increase.
As ATI problems have continued to proliferate, it has been found that common operating system programs have a tendency to cause a large number of writes to specific locations on hard drives. The data on the drives become corrupt when the excessive writes occur, and this often makes the systems unbootable. Indeed, this problem is growing due to increased areal density and OS workload while, at the same time, programs that access and update the information on the hard drive frequently can cause ATI.